Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$139.39	10.229%	$153.6482	$153.65	$153.65	$153.60
Purchase #2	$188.53	6.144%	$200.1133	$200.11	$200.10	$200.10
Purchase #3	$150.94	5.228%	$158.8311	$158.83	$158.85	$158.80
Purchase #4	$64.37	4.288%	$67.1302	$67.13	$67.15	$67.10
Purchase #5	$80.53	6.691%	$85.9183	$85.92	$85.90	$85.90
Purchase #6	$245.55	10.665%	$271.7379	$271.74	$271.75	$271.70
Purchase #7	$214.30	11.603%	$239.1652	$239.17	$239.15	$239.20
7 purchase totals =	$1,083.61		$1,176.5442	$1,176.55	$1,176.55	$1,176.40